The method
Before using the result
- Nominal air changes assume a well-mixed enclosure. ACH is not effective contaminant removal, drying performance or a prescribed equipment count.
Worked examples
These original training examples illustrate the method for North American Technician Excellence Certification (NATE). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Check the relationship between a measured supply airflow and room volume. Use the nominal interval to explain air changes without promising complete pollutant removal.
- Room volume input
- Dimensions
- Room length
- 5 m
- Room width
- 4 m
- Room height
- 3 m
- Measured air volume flow
- 360 m³/h
- Room volume = 60 m³.
- ACH = 0.1 × 3600 / 60.
- Interval = 60 / 0.1 seconds.
- Room volume: 60 m³
- Air changes: 6 h⁻¹
- Nominal interval: 600 s
2. Comparison example
Compare a different supplied condition using the same method. For Technical Conquer, the important check is that the input meaning, units and method assumptions still match the problem.
- Room volume input
- Dimensions
- Room length
- 5 m
- Room width
- 4 m
- Room height
- 3 m
- Measured air volume flow
- 720 m³/h
- Room volume = 60 m³.
- ACH = 0.2 × 3600 / 60.
- Interval = 60 / 0.2 seconds.
- Room volume: 60 m³
- Air changes: 12 h⁻¹
- Nominal interval: 300 s
Check your understanding
1. Which relationship is used?
ACH = Q × 3600 / room volume; nominal interval = volume/Q.
2. Which assumption should you check first?
Nominal air changes assume a well-mixed enclosure. ACH is not effective contaminant removal, drying performance or a prescribed equipment count.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to North American Technician Excellence Certification (NATE) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.